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Abstract

Objectives

Mycophenolate mofetil (MMF) was reported to be a main cause of diarrhea following organ transplantation. However, research on MMF-induced diarrhea following allogeneic hematopoietic stem cell transplantation (allo-HSCT) is currently insufficient. This retrospective study examined the incidence of MMF-induced diarrhea among allo-HSCT recipients.

Methods

Recipients were divided according to the receipt of MMF and the appearance of diarrhea. The differences in clinical information, MMF usage and trough concentrations, and the occurrence of diarrhea from the first day of conditioning treatment to 100 days after transplantation were analyzed.

Results

In total, 32.9% of the recipients reported diarrhea. The incidence rate of diarrhea was higher in the MMF group than in the non-MMF group (40.0% vs. 16.7%). MMF-induced diarrhea usually occurred within 9 days of MMF initiation and persisted for 7.27 ± 3.54 days. The average body weight, MMF daily dose, and MMF trough concentration were higher in patients with diarrhea.

Conclusion

MMF increased the risk of diarrhea in allo-HSCT recipients, and the risk was related to the MMF dose and trough concentration. The difference in onset time could be a basis for identifying the cause of diarrhea in allo-HSCT recipients.

Keywords

Mycophenolate mofetil diarrhea allogeneic hematopoietic stem cell transplantation graft-versus-host disease granulocyte megakaryocyte conditioning

Introduction

Diarrhea is a common gastrointestinal complication after solid organ transplantation, occurring in up to 40% of liver transplant recipients¹ and 9% to 30% of renal transplant recipients.² Based on Medicare claims in the United Network for Organ Sharing registry, the cumulative incidence of diarrhea is reported to be 11.5%, 17.5%, and 22.6% at 1, 2, and 3 years, respectively, after renal transplantation.³ Infection, medication, and graft-versus-host disease (GVHD) can all lead to transplant-related diarrhea. Since its approval in 1995, mycophenolate mofetil (MMF) has been one of the most widely used immunosuppressive drugs in both solid organ transplantation and allogeneic hematopoietic stem cell transplantation (allo-HSCT). MMF is also frequently reported to be associated with diarrhea as an adverse reaction in transplant recipients. In renal transplant recipients treated with MMF, the incidence rate of diarrhea ranges from 12.7% to 37.3% when combined with cyclosporine and 29.1% to 63.8% when used with tacrolimus.^4–7 Diarrhea is also a common complication during allo-HSCT, with an average incidence of approximately 40% to 50%, and the risk is higher within the first several weeks post-transplantation.^8,9 High-dose chemotherapy, radiotherapy, infections, intestinal GVHD, or other causes can contribute to the risk of diarrhea in allo-HSCT recipients.^10–12 However, the occurrence of MMF-induced diarrhea in allo-HSCT recipients has not been sufficiently studied. Differentiating MMF-induced diarrhea from other causes of diarrhea in allo-HSCT recipients is difficult.¹³ Our study retrospectively analyzed data from an HSCT center in China to clarify the clinical features of MMF-induced diarrhea in allo-HSCT recipients to deeper our understanding of MMF-induced diarrhea in different populations during different periods after transplantation.

Materials and methods

Study design

This retrospective study was conducted in an HSCT center in China from 1 January 2018 to 31 December 2022. The reporting of this study conforms with the STROBE guidelines.¹⁴ This study was reviewed and approved by the ethical committee of Hainan General Hospital (approval number 2021-232). All patients were informed of the purpose of this study and the application of the data, and written informed consent was obtained from all participants. Patients receiving allo-HSCT during this time were eligible. Data including the clinical diagnosis, treatment plan, MMF usage, MMF trough concentration, and records of diarrhea were collected. The occurrence of diarrhea from the first day of conditioning treatment to 100 days after transplantation was compared between recipients who did or did not receive MMF. In addition, the onset time and duration of diarrhea, the stool properties, and other accompanied symptoms such as fever, nausea, vomiting, and abdominal pain during diarrhea were statistically analyzed.

Patient selection

Patients older than 14 years who were diagnosed with hematological diseases and who received allo-HSCT as treatment in Hainan General Hospital were eligible for entry. The exclusion criteria included a diagnosis of intestinal infections, the presence of Crohn’s disease or ulcerative colitis, and diarrhea before conditioning treatment. Patients treated with MMF were further divided into the diarrhea and non-diarrhea groups according to their medical record. All patient details were de-identified in the study.

MMF treatment plan

Patients accepting stem cells from haploidentical relatives or unrelated donors take MMF as a first-line immunosuppressant in our institution, usually in combination with cyclosporine or tacrolimus. The per-day dose of MMF given to recipients weighing more than 40 kg but less than 70 kg was 1 g. For patients weighing more than 70 kg, the MMF dosage was increased to 1.5 g per day. For patients weighing less than 40 kg, the MMF dosage was reduced to 0.5 g per day. MMF dispersible tablets were administered in two divided doses from day 7 or 9 before transplantation to day 30 after transplantation in the absence of serious GVHD.

Trough concentration of MMF

Two milliliters of serum were collected 30 minutes before patients took MMF on the eighth day, and the MMF concentration was determined by enzyme-amplified immunoassay using the mycophenolic acid assay (Siemens Healthineers, Erlangen, Germany) and the Viva-E system (Siemens Healthineers).

Definition of diarrhea

The definition of diarrhea in our study was three or more stools or liquid stools per day over 3 days.

Clinical assessments

The onset time and duration of diarrhea, stool properties, and accompanied symptoms lasting for more than 3 days were collected. Stool pathogenic cultivation was performed to detect intestinal infection. Acute GVHD (aGVHD) referred to GVHD occurring within 100 days after transplantation, usually involving the skin, liver, and upper or lower digestive tract. All patients underwent rigorous evaluation to detect aGVHD accompanied according to the Mount Sinai aGVHD International Consortium criteria.¹⁵ The median times of granulocyte and megakaryocyte implantation were also collected.

Statistical analysis

Continuous variables were presented as the mean and standard deviation. The onset times of diarrhea and aGVHD and timing of granulocyte and megakaryocyte implantation were expressed as the median. Statistical differences between groups were analyzed using the chi-square test and Mann–Whitney U test, with P < 0.05 indicating significance. All statistical analyses were performed using IBM SPSS 20.0 (IBM Corp., Armonk, NY, USA).

Results

Patient information

Seventy-nine allo-HSCT recipients were enrolled in this study. The cohort included 40 men and 39 women with a mean age of 29.97 ± 11.95 years. Fifty-five patients received MMF. The median patient ages in the MMF and non-MMF groups were 28 and 30 years, respectively. Meanwhile, 81.01% of the patients were diagnosed with leukemia, and 13.92% were diagnosed with severe aplastic anemia. In addition, 69.62% of the patients accepted haploidentical transplantation. The conditioning treatments were based on busulfan and cyclophosphamide (BUCY) without total body irradiation. The GVHD prevention schemes were based on cyclosporine/tacrolimus and low-dose methotrexate with or without MMF and anti-thymocyte globulin (ATG). The median times to granulocyte and megakaryocyte implantation in the MMF group were 14 and 15 days, respectively, versus 13 and 15 days, respectively, in the non-MMF group. Age, sex, weight, the median time to granulocyte implantation, and the receipt of an intensified therapeutic regimen consisting of BUCY, cytosine arabinoside (Ara-C), and other drugs (most patients received 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea) did not differ between the groups. The characteristics of the MMF and non-MMF groups are presented in Table 1.

Table 1.

Patient characteristics of the group with MMF and the group without MMF.

Basic items	MMF group (n = 55)	Non-MMF group (n = 24)	P
Sex
Male	31 (56.36%)	9 (37.50%)	0.123
Median age (years)	28	30	0.593
Age range (years)	15–56	15–57
Weight (kg)	55.62 ± 8.92	53.43 ± 6.77	0.122
Clinical diagnosis
Acute myeloid leukemia	17 (30.90%)	7 (29.16%)
Acute lymphoblastic leukemia	19 (34.54%)	11 (45.83%)
Mixed leukemia	0	1,4.17%
Chronic myeloid leukemia	7 (12.73%)	1 (4.17%)
Chronic myelomonocytic leukemia	1 (1.82%)	0
Myelodysplastic syndrome	1 (1.82%)	0
Non-Hodgkin’s lymphoma	2 (3.64%)	0
Severe aplastic anemia	7 (12.73%)	4 (16.67%)
Thalassemia	1 (1.82%)	0
Donor relationship
Syngeneic	5	23
Haploidentical	44	1
Unrelated	6	0
Stem cell source
Peripheral blood and bone marrow	32	8
Peripheral blood only	23	16
Conditioning treatment
BUCY + Ara-C + other drugs	30 (54.55%)	11 (45.83%)	0.476
Classic BUCY	11	8
Flu + BUCY + ATG	5	0
Flu + CY + ATG	1	0
BUCY + ATG	1	1
CY + ATG	0	3
RIC	1	1
Others	6	0
GVHD prevention scheme
CSA/TAC + ATG + MMF + MTX	43	0
CSA/TAC + MMF + MTX	12	0
CSA/TAC + ATG + MTX	0	5
CSA/TAC + MTX	0	19
Median time to granulocyte implantation (days)	14 (9–26)	13 (10–20)
Median time to megakaryocyte implantation (days)	15 (9–63)	15 (12–89)

Data are presented as n (%), median (range), or mean ± standard deviation.

BU, busulfan; CY, cyclophosphamide; Ara-C, cytosine arabinoside; FLU, fludarabine; ATG, anti-thymocyte globulin; CSA, cyclosporine A; MMF, mycophenolate mofetil; TAC, tacrolimus; MTX, methotrexate.

Other drugs included 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea, etoposide, and decitabine.

Twenty-six allo-HSCT recipients (32.9%) experienced 30 episodes of diarrhea during conditioning treatment and within 100 days after transplantation. Twenty-two patients (40.0%) reported 26 episodes (four were confirmed as aGVHD by colonic biopsy) of diarrhea in the MMF group, whereas only four patients (16.7%) reported four episodes of diarrhea in the non-MMF group (P = 0.012). Then, patients in the MMF group were further divided into diarrhea (n = 22) and non-diarrhea groups (n = 33). Sex, age, duration of MMF usage, the proportion of patients undergoing haploidentical transplantation, the incidence rate and onset time of aGVHD, and the median times to granulocyte and megakaryocyte implantation did not differ between these groups. However, average body weight (59.45 ± 10.31 kg vs. 52.94 ± 6.74 kg, P < 0.05), the MMF daily dose (1113.64 ± 214.47 mg vs. 969.70 ± 121.15 mg, P < 0.05), and the MMF trough concentration (0.59 ± 0.44 μg/mL vs. 0.31 ± 0.18 μg/mL, P < 0.05) were significantly higher in the diarrhea group than in the non-diarrhea group. The median time to megakaryocyte implantation was longer in the diarrhea group, but the specific reasons and significance were not clear. The comparison data are presented in Table 2.

Table 2.

Characteristics of the diarrhea and non-diarrhea groups.

Basic items	Diarrhea group (n = 22)	Non-diarrhea group (n = 33)	P
Sex
Male	14	17	0.375
Mean age (years)	30.50 ± 12.21	28.55 ± 12.25	0.508
Age range (years)	16–56	15–56
Weight (kg)	59.45 ± 10.31	52.94 ± 6.74	0.016
Daily dose of MMF (mg)	1113.64 ± 214.47	969.70 ± 121.15	0.003
Trough concentration of MMF (μg/mL)	0.59 ± 0.44	0.31 ± 0.18	0.002
Duration of MMF therapy (days)	52.59 ± 20.39	53.39 ± 15.67	0.803
Haploidentical transplantation	16	28	0.449
Combined treatment with CSA	20	31	0.672
aGVHD	8	11	0.152
Median onset time of aGVHD (days)	24 (10–60)	18 (12–76)	0.090
Median time to granulocyte implantation (days)	14 (9–26)	14 (10–20)	0.667
Median time to megakaryocyte implantation (days)	19 (10–57)	14 (9–63)	0.032

MMF, mycophenolate mofetil; CSA, cyclosporine A; aGVHD, acute graft-versus-host disease.

The median latency between the use of MMF and the onset of diarrhea was 9 days. Diarrhea lasted on average for 7.27 ± 3.54 days (range, 3–15 days; Table 3). In total, 50.0% of cases of MMF-induced diarrhea occurred within the first 7 days after transplantation. In total, 26 episodes of aGVHD were recorded, and the median onset time was 17 days after transplantation, with 73.1% of events occurring between days 8 and 30. The onset time of MMF-induced diarrhea, the onset time of aGVHD, and the times to granulocyte and megakaryocyte implantation are presented in Figure 1. MMF-induced diarrhea usually occurred before granulocyte and megakaryocyte implantation, generally occurring in the first week after transplantation and approximately 9 days after starting MMF therapy. It was also confirmed that aGVHD was caused by allogeneic stem cells, which happened after implantation. The difference in onset time could serve as one of the references for distinguishing MMF-induced diarrhea from intestinal aGVHD.

Table 3.

Timing of diarrhea and aGVHD onset relative to transplantation.

Time relative to transplantation	Onset of diarrhea (n = 22)	Onset of aGVHD (n = 26)
Days −9 to 0	7	0
Days 1 to 7	11	0
Days 8 to 14	2	9
Days 15 to 30	2	10
Days 31 to 100	0	7

Day 0 indicates the day of transplantation.

Figure 1.

Onset times of diarrhea, aGVHD, and granulocyte and megakaryocyte implantation. aGVHD, acute graft-versus-host disease.

In total, 59.1% of cases of diarrhea were watery, and the most common accompanying symptom was abdominal pain (50.0%). Fever was present in 13.6% of the patients, whereas nausea and vomiting were rare. Unlike intestinal aGVHD, MMF-induced diarrhea was rarely accompanied by rash.

Discussion

The recognition and management of diarrhea before, during, and after allo-HSCT have gained increasing importance as indications and techniques of transplantation have expanded in recent decades.

Diarrhea occurs in almost half of patients receiving high-dose conditioning chemotherapy and radiotherapy. The toxicity of pretreatment regimens can cause diarrhea attributable to mucosal inflammation within the first 2 weeks after transplantation.¹⁰ However, almost all patients in our study received BUCY as the most basic conditioning regimen, and nausea and vomiting caused by these drugs were more pronounced. Meanwhile, patients receiving an intensified therapeutic regimen consisting of BUCY, Ara-C, and other drugs exhibited no significant differences. Therefore, conditioning treatment was unlikely to be the main factor leading to differences in the incidence of diarrhea between the MMF and non-MMF groups. Woillard’s multivariate analysis revealed that patients taking tacrolimus had a 2.8-fold risk of diarrhea than those taking cyclosporine following renal transplantation.¹⁶ However, less than 1% of our patients used tacrolimus with MMF, and thus, tacrolimus was unlikely to be the main cause of the increased incidence of diarrhea in this study.

aGVHD is the most common cause of diarrhea after implantation (>15 days) in allo-HSCT recipients, especially if diarrhea persists or new diarrhea develops beyond 3 weeks after HSCT.¹⁵ The symptoms of intestinal aGVHD vary from watery to bloody diarrhea associated with a high volume and abdominal pain or cramping. If the upper gastrointestinal tract is involved, patients might develop nausea, vomiting, and anorexia. Other features of aGVHD such as skin rash could also arise.¹¹ The incidence rate of aGVHD in the study was 32.9%, and 15.4% (four episodes) of these events were confirmed as intestinal aGVHD.

Infectious etiologies accounted for approximately 10% to 15% of cases in HSCT recipients.¹⁰ Van Kraaij et al. reported a much lower incidence of diarrhea attributable to intestinal infection in HSCT recipients (6%), and no pathogens were isolated in stool specimens from 46 HSCT recipients with acute diarrhea.⁹ All patients with diarrhea underwent stool property testing and pathogenic cultivation, but no pathogens were found. In addition, the preventive use of antibiotics was common in our unit, which might have increased the difficulty of pathogen cultivation. However, the long-term and extensive use of antibiotics can lead to infection by Clostridium difficile, which was the leading cause of infectious diarrhea among hospitalized patients. Prior research reported that the overall 1-year incidence of C. difficile infection (CDI) was 9.2% among HSCT recipients. The median time to diagnosis of CDI was 33 days after allo-HSCT. The authors found a strong relationship between early CDI and the subsequent development of gastrointestinal tract GVHD.¹⁷ Unfortunately, we could not test C. difficile toxin in stool culture in our hospital, representing one limitation of our study. However, CDI was indeed a potential cause of diarrhea, but it might have occurred more than 1 month after transplantation. We need to conduct further research based on routine C. difficile toxin testing to better distinguish the causes of diarrhea.

Squifflet and colleagues found that the incidence of diarrhea was dose-dependent, being higher in renal transplant recipients who received 2 g of MMF than in those who received 1 g of MMF (42.3% vs. 29.1%) when administered with a low dose of tacrolimus.⁷ The present study also revealed that MMF-induced diarrhea was dose-dependent and concentration-dependent in allo-HSCT recipients, being particularly common among patients receiving a daily dose exceeding 1.5 g. The diarrhea group had a higher MMF daily dose and MMF trough concentration than the non-diarrhea group because of the higher weight of the former group. In fact, all patients taking 1.5 g of MMF per day experienced diarrhea. However, the area under the curve of MMF (AUC_0-12h) was reported to be more closely related to drug exposure and adverse reactions.^18,19 The therapeutic window of 30 to 60 mg·hour/L AUC_0-12h proposed by the Transplantation Society since 2008 remained acceptable in solid organ transplant recipients who have a low-to-intermediate immunologic risk after transplantation.²⁰ AUC_0-12h lower than 30 mg·hour/L was clearly associated with an increased risk of acute rejection, and a value exceeding 60 mg·hour/L could lead to side effects. However, the most suitable AUC range for allo-HSCT recipients remains unclear.

One limitation of this study was that AUC of MMF was not fully applied because the exposure correlation between AUC and MMF was better than the trough concentration. We are establishing a calculation formula for AUC in allo-HSCT recipients, and we hope that this part of the study can guide adjustment of the MMF dosage to avoid the occurrence of diarrhea in the future.

In conclusion, MMF increased the risk of diarrhea in allo-HSCT recipients from 16.7% to 40.0% in this study, and the increased risk was related to the dose and trough concentration of MMF. MMF-induced diarrhea usually lasted for 7.27 ± 3.54 days, and most events occurred within the first 9 days after transplantation, presenting earlier than the onset of aGVHD and granulocyte and megakaryocyte implantation. The difference in onset time could be a primary basis for identifying the cause of diarrhea in allo-HSCT recipients.

Footnotes

Acknowledgements

We thank all patients who participated in this study.

Author contributions

Liangmo Lin contributed to research design and data analysis, and she drafted the manuscript. Mianhui Hong contributed to medical record retrieval and data registration. Xiangjun Fu was responsible for the diagnosis and management of patients.

Data availability statement

All data supporting this study will be available from the authors.

Declaration of conflicting interests

The authors declared that they have no competing interests.

Funding

This study was supported by the Hainan Provincial Natural Science Foundation of China (Study on the mechanism of mycophenolic acid induced diarrhea in hematopoietic stem cell transplantation) (grant number 822QN452).

ORCID iD

Liangmo Lin

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Mycophenolate mofetil increases the risk of diarrhea in allogeneic hematopoietic stem cell transplantation recipients

Abstract

Objectives

Methods

Results

Conclusion

Keywords

Introduction

Materials and methods

Study design

Patient selection

MMF treatment plan

Trough concentration of MMF

Definition of diarrhea

Clinical assessments

Statistical analysis

Results

Patient information

Discussion

Footnotes

Acknowledgements

Author contributions

Data availability statement

Declaration of conflicting interests

Funding

ORCID iD

References